Advanced augmentors are being required to operate with increasingly high inlet gas temperatures. These augmentors may be subjected to gas temperatures entering the augmentor exceeding 2200 degrees F. Although these high gas temperatures would result in immediate fuel auto ignition, a flame stabilization system is required to obtain and maintain a stable flame during lower inlet temperature conditions that exist at high altitude low aircraft velocity operation.
At these very high levels of inlet temperature conventional augmentor flame holding systems are not suitable. They will experience long term operation at high temperature and will operate at extremely high temperatures when the augmentor is in operation. Even with part load augmentor operation extremely high local temperatures are experienced which should preferably be limited to easily maintained portions of the augmentor arrangement.
Systems introducing fuel upstream of the spray bar provide an ignitable mixture throughout a wide range of the duct. With auto ignition conditions existing conventional spray bars can possibly lead to instability and screech of the flame as it randomly propagates through the mixture. A more controlled rapid burning of the fuel is desirable.
With the limited flow area available and the high velocities existing, unnecessary flow blockage of the duct is detrimental. In addition to generating unacceptably high parasitic pressure losses, high blockage designs are more prone to screech instabilities. Accordingly, a flame holding system which minimizes significant flow blockage is desirable.